This is a continuation of a long-term endeavor to understand the visual cortex of cats and monkeys in terms of its single-cell physiology, and the groupings of cells according to their physiological properties. We wish to learn more, in both area 17 and 18, about the relationships between the different groupings, particularly between orientation columns, ocular dominance columns, and the recently discovered cytochrome blobs. The blobs are distinguished from the background by a number of enzymatic stains, by 2-deoxyglucose, and by proline injection into the eye or the lateral geniculate body. We plan to study the single-cell physiology of these structures, comparing receptive fields of cells within and outside the blobs. We will examine their inputs, outputs, and intrinsic connections, using a variety of anatomical methods: the Nauta method, retrograde transport of horseradish peroxidase, orthograde transport of aminoacide, and the Golgi technique. We will study their enzyme histochemistry, development, and differences in different species including normal and blind or amblyopic humans.